[Leica] The Tele elmarit 135 Is So A Real Pooch of a Lens

[henningw at archiphoto.com (Henning Wulff)]

At 10:15 AM -0800 1/5/08, wildlightphoto@earthlink.net wrote:
>Raimo K <raimo.m.korhonen@uusikaupunki.fi>
>
>>Since when do they use this designation?
>
>Since 1984 at least if not earlier.
>
>Doug Herr
>Sacramento
>http://www.wildlightphoto.com
>
>>
>>----- Original Message -----
>>From: <wildlightphoto@earthlink.net>
>>To: "Leica Users Group" <lug@leica-users.org>
>>Sent: Saturday, January 05, 2008 3:17 PM
>>Subject: Re: [Leica] The Tele elmarit 135 Is So A Real Pooch of a Lens
>>
>>
>>>  Raimo K <raimo.m.korhonen@uusikaupunki.fi> wrote:
>>>
>>>>APO means apochromatic correction of the lens, there are no apochromatic
>>>>elements.
>>>
>>>  In Leica's case, APO is the designation they use for the extra-low
>>>  dispersion glass which their optical designers feel is essential to
>>>  designing lenses with apochromatic performance.  This is like Nikon's 
>>> use
>>>  of the ED designation for their extra-low dispersion glass.  Raimo is
>>>  correct that there are no apochromatic elements, but there is APO glass
>>>  which is used to design apochromatic lenses.
>>>


In Leica's case they also use the term correctly. They use the APO 
designation to indicate apochromatic correction. Yes, in many cases 
special low dispersion glasses can help to achieve this, but low 
dispersion or anomalous dispersion glass is not essential for 
apochromatic correction.

Leica uses low dispersion glasses on various non-apochromatic lenses as well.

-- 
    *            Henning J. Wulff
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